Larger helicopters, in general, have several features in common in a typical basic configuration or layout. For instance, a typical helicopter will have a cabin section rearward of the pilot's cockpit or flight deck and which is used to transport people, cargo or both. In addition, the helicopter will have an engine compartment which is located typically above and to the rear of the pilot's cockpit or flight deck, and above the cabin section. The engine compartment typically houses two primary components, at least one engine and a rotor transmission with a corresponding transmission housing.
Both the engine and the rotor transmission contain numerous fluids, such as petroleum-based lubricants, that are critical to the operation of the engine and the transmission. These fluids inevitably leak from various locations in the engine and the transmission during both the operation and storage of the helicopter. Because the engine compartment is generally oriented above the cabin section, any leaking fluids eventually seep or drip into the cabin section, unless proper sealing mechanisms are in place. The inflow of these leaking fluids spoil, stain or damage the cabin's interior materials such as seat covers and acoustic linings. In addition, the leaking fluids can severely damage or destroy sensitive electronic equipment that may be placed in the cabin section of a helicopter.
Moreover, the exterior of the helicopter around the engine and transmission compartment is not completely fluidtight, allowing fluid such as water to leak from these areas into the cabin with similar adverse effects.
During routine inspection and maintenance it is necessary to have both ready visual and physical access to portions of the engine or at least the rotor transmission. Such access is required to check critical fluid levels, to replace worn, damaged or depleted parts or filters, or to adjust mechanical systems. Typically, various access panels in or around the engine or transmission compartments provide the requisite openings to achieve ready access to the engine and the rotor transmission. In some helicopters, a forged or fixed airframe structure forms an access opening which is located below the rotor transmission housing and above the cabin section. The opening is thus accessible through the cabin's ceiling. This access opening, however, must be sealed by a cover against the inevitable oil and fluid drippings which the engine and the rotor transmission will produce, as well as against water leakage.
The access opening below the engine compartment in prior helicopters, such as the BLACK HAWK® helicopter, made for the United States by Sikorsky Aircraft Company of Stratford, Conn., is defined by both the aircraft structural forgings and a flexible or yieldable downwardly-turned skirt which is riveted onto the helicopter's forged structure. The skirt is thin and many times more flexible relative to the helicopter's forged structure.
Prior drip pan designs attached a covering plate directly to the flexible skirt with a hollow seal sandwiched therebetween. One hollow seal used in prior designs resembled the flexible, hollow door seals used around car doors or refrigerator doors. However, the skirt contains surface aberrations, such as the protruding rivet heads from the rivets securing the skirt to the forged helicopter structure. When the seal engaged both the skirt and the rivet heads, it could be upset enough so that leakage occurred. Accordingly, the hollow seal traversing these aberrations while sandwiched between the skirt and the covering plate is unable to provide a suitable, consistent, long-term fluid seal. Moreover, flexing of the flexible skirt could also cause leakage.
Also, the geometry of the cover cannot be such that it protrudes significantly into the interior of the cabin section. Headroom in the cabin section typically is limited and any additional protrusion from the ceiling of the cabin section is undesirable. In addition, because weight is critical to the operation of any aircraft, heavy cover constructions are undesirable.
Other prior drip pan structures disclosed in U.S. Pat. Nos. 6,112,856; 6,216,823; and 6,446,907 and Design Pat. No. D444,443, which are fully incorporated herein by this express reference, provided improvements and solutions to these difficulties.
In addition, Sikorsky more recently introduced its “M” Model BLACK HAWK® helicopter for which these prior structures were not readily adaptable due to a change in configuration of the skirt noted above. In particular, while the prior drip pans provided a port for visual access to an oil filter, the port was offset from the filter, rendering it more difficult to see the filter from many viewing angles through the port, requiring specially shaped tools to manipulate filter retention bolts, and requiring tilting of filters when removed or replaced.
The “M” model was introduced by Sikorsky for use by U.S. Military. In that model, and in other aircraft with what are or will be similarly-shaped skirts, there is a skirt as disclosed in U.S. Pat. No. 8,096,496 with an access area or corner for the filter which is pulled outwardly to allow direct and straight-through access to the filter and its filter retention bolts when the pan is removed. Such direct access is preferable as it eliminates the need for the special dog-bone shaped tools necessary to operate the filter retention bolts to remove and install the filter as was required with the prior drip pan, which not only required such tools but also required the filter to be “tipped” as it was removed or replaced and before it could be seated (see FIG. 6 of U.S. Pat. No. 6,446,907). Accordingly, in the new “M” model, one corner has been pulled or extended outwardly and asymmetrically to the other corners. Stated in another way, the radius point or center of the expanded corner curve of the skirt has been moved outwardly from its position in the prior drip pan and the straight sides of the skirt are no longer tangent to the curve of this corner.
The problems associated with the asymmetrical nature of the skirt, which takes on inwardly-facing convex shapes, directed inwardly of the access opening, before flowing into an expanded inwardly-facing concave corner in the “M” model were overcome by a drip pan apparatus disclosed in U.S. Pat. Nos. 8,096,496 and 8,317,127 while still forming a leak-proof seal of the access opening in spite of the previously experienced difficulties with forming a face seal in this location. Furthermore, the drip pan apparatus disclosed is cost effective and easily installed while also facilitating maintenance of the rotor transmission and particularly easing access to the filter secured to the rotor transmission. Moreover, the visual access to the filter through the corresponding site port was also solved.
Nevertheless, despite the significant improvement provided by the drip pan apparatus, modifications to the rotor transmission of the BLACK HAWK® helicopter, including model variations thereof, may slightly alter the position of the filter on the transmission. For example, the rotor transmission found in the S70A-09 helicopter, made for the Australian Army by Sikorsky is modified for applications specific the Australian Army's use. It is believed these slight modifications to the rotor transmission include a slight decrease in clearance between the oil filter and the skirt encircling the access opening for the rotor transmission. While the decrease in clearance is small, possibly amounting to an inch or less, access to the oil filter is hampered, even in situations in which the drip pan apparatus disclosed in U.S. Pat. No. 8,096,496 is utilized. Thus, there is a need for an improved drip pan apparatus for sealing the access opening of a rotor transmission in a helicopter, such as the S70A-09 Australian Army helicopter that utilizes the asymmetrical skirt found in the “M” Model BLACK HAWK® helicopter, that facilitates visual inspection of the rotor transmission, including inspection of the oil filter, and that facilitates and reduces maintenance time, while also sealing the access opening from leakage.
Accordingly, it is one objective to provide an improved leak-proof drip pan apparatus for use in an “M” model BLACK HAWK® helicopter or another helicopter, such as the Australian Army's S70A-09 helicopter, which shares a similar configuration of the skirt surrounding the access opening to the rotor transmission.
A further objective of this invention is to provide an improved cover and seal for the interior access opening of helicopters such as the BLACK HAWK® “M” model helicopter and those of similar structure, such as the Australian Army's S70A-09 helicopter.
Another object of this invention is to provide a drip pan that will effectively and consistently seal fluid from passage from an engine or transmission compartment to a cabin section of a BLACK HAWK® “M” model helicopter and similar air frames, such as the Australian Army's S70A-09 helicopter.
Another object of this invention is to provide a drip pan which permits quick visual and physical access to the engine or transmission compartment of a BLACK HAWK® “M” model helicopter and similar helicopters, such as the Australian Army's S70A-09 helicopter, without requiring modification to the existing aircraft structure.
Another objective of the invention is to more effectively seal a drip pan to the skirt defining a transmission access opening in a BLACK HAWK® “M” model helicopter and similar helicopters, such as the Australian Army's S70A-09 helicopter.
Still another object of this invention is to provide a drip pan that can be attached to the existing structure of a BLACK HAWK® “M” model helicopter and similar helicopters, such as the Australian Army's S70A-09 helicopter, with only slight modifications of the existing air frame structure and with minimal intrusion into the helicopter's cabin section.
Another objective of the invention is to provide an improved drip pan for use with a BLACK HAWK® “M” model helicopter and similar air frames, such as the Australian Army's S70A-09 helicopter, using an o-ring seal between drip pan and frame, where all peripheral curves in the pan are convex (i.e., outwardly directed) with respect to the pan.
Yet another objective of the invention is to provide enhanced visual access to a filter in an “M” model BLACK HAWK® helicopter and similar air frames, such as the Australian Army's S70A-09 helicopter.